During the operation of the electromagnetic switches, the flux linkage can replace the mechanical parameters to characterize the motion of the actuator. But the observation errors of the flux linkage will lead to a failure of the control strategy. To address this issue, a cascade control strategy based on flux linkage slope is proposed. The observed flux linkage is intercepted by a sliding window, the flux linkage slope is calculated, then the flux linkage slope is used to establish a cascade control strategy. This strategy consists of an outer loop of the flux linkage slope and an inner loop of the coil current. The theoretical deduction proves that the flux linkage slope can be compatible with the flux linkage observation error and reflect the change of the real flux linkage caused by the motion of the armature. The simulation results show that the proposed cascade control strategy has good compatibility with the flux linkage observation error while realizing the self-adjusting of coil current with the displacement of the armature.